The tire pressure is decisive for the ability to use a pneumatic tire. It is therefore set according to specifications and has to be regularly checked and, if appropriate, adjusted in order to maintain the functional capability. The tire pressure can also increase during operation as a result of warming. An incorrect tire pressure leads to premature wear or to the pneumatic tire failing. For this reason, tire pressure-monitoring systems are being increasingly used in passenger cars. Tire pressure-monitoring systems serve to monitor the tire pressure in motor vehicles in order to minimize and to detect early accidents caused by incorrect tires. In addition, there can be a saving in petrol with the optimum tire pressure, and unnecessary tire wear can be avoided.
In direct measuring systems, a pressure sensor senses the air pressure and the air temperature of a tire. This information is transmitted, together with an identifier, to a control unit in the vehicle by radio at specific intervals. These systems may detect slow or even rapid pressure losses in all tires since they monitor the pressure directly. Depending on the display concept, the driver is provided with information about the current pressure value in plain text, which he either sees continuously on the display or can interrogate by means of the pressure button, or else he only receives a warning when the tire pressure is too low.
Tire pressure-monitoring systems of the latest generation also have a “left/right rotation detection”. This means that any of the four wheel electronic systems located on the vehicle also transmits, in its transmission protocol, the direction of rotation of the tire. The control unit of the tire pressure-monitoring system can therefore assign which of the wheel electronic systems is installed on the right or left of the vehicle. Since this “left/right rotation detection” is measured with acceleration sensors, this technology functions in practice usually only on roads with a smooth or level covering. On roads or paths with an uneven or poor underlying surface covering an incorrect assignment of the corresponding wheel positions or incorrect measurement results may occur owing to excitations/vibrations of the wheel electronic system or the acceleration sensors.